Several technologies to ensure visibility of a display unit of a mobile terminal, such as a mobile phone, are known. One is a technology of controlling a luminance in the display unit according to brightness of ambient light. Another is a technology of displaying an image on a large screen having a plurality of display areas (display panels).
For example, Patent Literature 1 discloses a mobile phone including first and second display units and an optical sensor. When brightness measured by the optical sensor is equal to or lower than a predetermined value, the mobile phone automatically causes the second display unit to display no image, and causes only the first display unit to display an image while decreasing a luminance in a backlight corresponding to the first display unit. This technology reduces glare occurring when a user views an image on a screen in a dark place, and thus ensures visibility of the screen in the dark place. This technology also reduces power consumption in displaying an image.